1. Field of the Invention
This invention relates to row at a time electron beam addressed storage target configurations and their applications.
2. Prior Art
Several electron beam addressed storage target configurations have been utilized in spatial light modulator applications. See for instance U.S. Pat. No. 4,387,964 to Arrazola et al, Jun. 14, 1983.
As quoted from the book "Electronic Image Storage" by B. Kazan and M. Knoll, page 105, Section b, titled "Equilibrium Writing by Barrier-Grid (Collector) Modulation", "In operation it may not always be possible (or practical) to provide sufficient current in a single scan to shift each target element completely to the equilibrium potential." As to be shown herein, my invention utilizes row at a time addressing of the electron beam storage target. Row at a time addressing could increase the duration an electron beam bombards a particular location on a storage target as compared to serial electron beam scanning. The uninterrupted time or duration an electron beam bombards the same location on a target will be referred to herein as dwell time.
In my invention, dwell time could equal the active line time of a row addressed display. Increasing the dwell time, for a given current level, could allow more charge to be transferred to every pixel element in each row p which is being bombarded by a respective electron beam on a row at a time basis. Consequently, my invention provides latitude which could enhance the performance attainable in applications which employ electron beam addressed storage targets. Utilizing my invention, to dramatically increases the dwell time over previous implementations, could enhance a target pixel's ability to achieve an equilibrium potential within a single addressing interval.
Alternatively, by increasing the dwell time, the current necessary to achieve a desired equilibrium level could be reduced. As to be shown herein, reducing current levels in an electron beam addressed device could enhance several aspects including increasing the spatial resolution attainable in the storage target. In addition, by increasing the dwell time for a given current level, more charge could be transferred to pixel elements of the target. Consequently, my invention could extend the voltage range of storage target operation since more charge could be supplied to allow pixel elements to attain a higher voltage level. This could broaden the scope of materials suitable for use in the storage target configurations of my invention. Broadening the scope of materials suitable for use in applications involving electron beam addressed storage targets could enhance performance attainable.
Furthermore, as to be described herein, several additional benefits exist to row at a time electron beam addressing utilized in my invention. Several advantages of row at a time electron beam addressing in my invention could be similar to the benefits provided by row at a time addressing utilizing thin film transistors. Such advantages could include a reduction of the bandwidth requirements for target components. Such advantages could include reduced dimensions associated with column electrodes in the storage target of my invention. Such reductions could enhance spatial resolution.
Additional spatial light modulators configurations which involve electron beam addressing include U.S. Pat. No. 3,971,931 to Jehle, Jul. 27, 1976. U.S. Pat. No. 3,971,931 did not include an electron collector or grid in the target configuration. As to be shown herein, my invention utilizes an electron collector as part of the target to provide a storage function. Consequently, as to be described herein, my invention could enhance luminous efficiency and/or simply the write/erase process associated with updating the target.
Additional row at a time electron beam addressed spatial light modulators include U.S. Pat. No. 5,196,767 to Leard et al, Mar. 23, 1993. As identified in the article "Field-Emitter Arrays for Vacuum Microelectronics" by C. A. Spindt et al, IEEE Transactions on Electron Devices, Vol. 38, No. 10, Oct. 1991, uniformity of such arrays could be an important consideration for defining performance attainable in applications which employee field emitter arrays. As to be shown herein, by utilizing the mode of operation available with the storage target configuration of my invention, variations in emission characteristics of field emitter arrays, or for that matter any electron beam source compatible with the addressing requirements of my invention, could manifest themselves as a variations in the charging time to achieve a desired potential difference across a target pixel. If the dwell time is at least as large as the maximum charge time, due to the lowest emission emitter and largest potential difference to charge, then such variations would be reduced in their effect, since the desired value is established within a row period and is essentially maintained for the remaining frame time. This is in contradistinction to spatial light modulators which utilize field emitter arrays, and interface field emitter arrays to electron beam addressed targets which incorporate different writing methods to achieve storage. Consequently, the storage target configurations of my invention could provide several benefits including enhanced luminous efficiency due to storage, improved uniformity of targets which are interfaced to row addressed electron beam sources while relieving the performance demands placed on row addressed electron beam source arrays, provide addressing convenience by combining the write/erase functions and extending the realm of high voltage target operation and/or enhancing the spatial resolution attainable in the target.
Additional electron beam addressed devices include U.S. Pat. No. 4,884,874 to Buzak et al, Dec. 5, 1989. Utilization of two electron beam guns fails to combine the write/erase functions and complicates packaging considerations of the spatial light modulator. As to be shown herein, several electron beam sources exist which are compatible with the row at a time addressing sequence of my invention and which could enhance packaging of spatial light modulators. Such sources include field emitter arrays. Relative packaging advantages of field emitter arrays are identified in U.S. Pat. No. 3,500,102 to M. E. Crost et al, Mar. 10, 1970.